Transistors are semiconductor devices that are commonly found in a wide variety of integrated circuits. When a voltage is applied to a gate of the transistor that is greater than a threshold voltage, the transistor is turned on, and current may flow through the transistor. When the voltage at the gate is less than the threshold voltage, the transistor is off, and current does not flow through the transistor.
One type of transistor is a TFET. TFETs switch from off to on by modulating tunneling through a barrier. Source and drain terminals of a TFET are doped of opposite type. A common TFET device structure consists of a P-I-N (p-type, intrinsic, n-type) junction, in which the electrostatic potential of the intrinsic region is controlled by a gate terminal.
The TFET is operated by applying gate bias so that electron accumulation occurs in the intrinsic region. At sufficient gate bias, band-to-band tunneling occurs when the conduction band of the intrinsic region aligns with the valence band of the P region. Electrons from the valence band of the p-type region tunnel into the conduction band of the intrinsic region and current can flow across the device. As the gate bias is reduced, the bands become misaligned and current can no longer flow.